WEBVTT - What makes your knuckles pop?

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<v Speaker 1>from how Stuff works dot com where smart Happens. I

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<v Speaker 1>am Marshall Brain with today's question, what makes your knuckles pop?

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<v Speaker 1>If you've ever laced your fingers together, turns your palms

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<v Speaker 1>away from you and bent your fingers back, you know

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<v Speaker 1>what knuckle popping sounds like. Joints produced that crack when

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<v Speaker 1>bubbles burst in the fluids surrounding the joint. Joints are

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<v Speaker 1>a meeting point between two separate bones, held together and

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<v Speaker 1>in place by connective tissues and ligaments. All of the

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<v Speaker 1>joints in our bodies are surrounded by synovial fluid, a thick,

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<v Speaker 1>clear liquid. When you stretch or bend your finger to

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<v Speaker 1>pop the knuckle, you're causing the bones of the joint

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<v Speaker 1>to pull apart. As they do this, the connective tissue

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<v Speaker 1>capsule that surrounds the joint is stretched. By stretching this capsule,

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<v Speaker 1>you increase its volume, and, as we know from chemistry class,

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<v Speaker 1>with an increase in volume comes a decrease in pressure.

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<v Speaker 1>So as the pressure of the synovial fluid drops, gas

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<v Speaker 1>is dissolved in the fluid become less soluble, forming bubbles

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<v Speaker 1>through a process called cavitation. When the joint is stretched

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<v Speaker 1>far enough, the pressure in the capsule drops so low

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<v Speaker 1>that these bubbles burst, producing the pop that we associate

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<v Speaker 1>with knuckle cracking. It takes about five to thirty minutes

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<v Speaker 1>for the gas to redissolve into the joint fluid. During

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<v Speaker 1>this period of time, your knuckles won't crack again. Once

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<v Speaker 1>the gas is dissolved, cavitation is once again possible, and

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<v Speaker 1>you can start popping your knuckles again. As for the

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<v Speaker 1>harms associated with this habit, according to Anatomy and Physiology

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<v Speaker 1>Instructors Cooperative, only one in depth study regarding the possible

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<v Speaker 1>detriments of knuckle popping has been published. This study, done

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<v Speaker 1>by Raymond Broder and published in the Journal of Manipulative

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<v Speaker 1>and Physiological Therapeutics, examine three hundred knuckle crackers for evidence

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<v Speaker 1>of joint damage. The results revealed no apparent connection between

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<v Speaker 1>joint cracking and arthritis. However, habitual knuckle poppers did show

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<v Speaker 1>signs of other types of damage, including soft tissue damage

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<v Speaker 1>to the joint capsule and a decrease in grip strength.

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<v Speaker 1>This damage is most likely a result of the rapid,

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<v Speaker 1>repeated stretching of the ligaments around the joint. On the

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<v Speaker 1>positive side, there's evidence of increased mobility and joints right

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<v Speaker 1>after popping. When joints are manipulated, the gold g tendon organs,

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<v Speaker 1>a set of nerve endings involved in humans motions, sense

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<v Speaker 1>are stimulated and the muscles surrounding the join to relax.

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<v Speaker 1>This is part of the reason why people can feel

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<v Speaker 1>loose and invigorated after leaving a chiropractor's office where a

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<v Speaker 1>cavitation is induced as part of the treatment. Backs, knees, elbows,

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<v Speaker 1>and all other movable joints are subject to the same

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<v Speaker 1>kind of manipulation as knuckles are. Do you have any

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<v Speaker 1>ideas or suggestions for this podcast? If so, please send

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<v Speaker 1>me an email at podcast at how stuff Works dot com.

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